Abstract
Hydraulic dynamic seals for reciprocating or alternating motion are machine elements with widespread applications in the automotive, aerospace, marine, pharmaceutical and several other industrial sectors. They have been under commercial development for many decades, and are often met in critical positions, consuming a considerable amount of energy during operation. An objective function of mass leakage rate, friction force and an abrasive-wear representative term is proposed in the present study to evaluate the performance of hydraulic, polymeric sliding seals under suitable constraints. Using Variational Calculus, analytical and numerical techniques, the objective function is minimized, resulting in an optimal seal profile that maximizes sealing performance for given, steady-state operating conditions, in additional consideration of the structural integrity and manufacturability of the modified seal. The obtained seal shape and related pressure distribution are reminiscent of those for U-cup and step seals, designs that dominate the industry. In the course of the mathematical analysis, some major obstacles are documented that show how sensitive and complicated sealing performance really is.
Highlights
Several theoretical studies in the past 20 years have focused on the performance of hydraulic dynamic seals in an effort to produce experimentally verifiable results
Three evaluators of sealing performance are of importance in this optimization study, namely the mass leakage rate, the friction force and the abrasive wear
For the sake of this example, the maximum acceptable mass leakage rate and friction force are set equal to 30 mg/s and 80 N, respectively, both values in the order of magnitude of those expected for similar sealing applications [7,8]
Summary
Several theoretical studies in the past 20 years have focused on the performance of hydraulic dynamic seals in an effort to produce experimentally verifiable results. Lubricants 2020, 8, 40 usually less than 1 μm, the performance of the seal for given operating conditions is established in terms of mass leakage rate, frictional force and abrasive wear rate of the tribopair It is imperative for any theoretical analysis to focus on the inlet zone where the secret of sealing success or even failure normally lies. Minimizing leakage for given seal geometry is achieved by reducing the average film thickness in the sealing contact (e.g., by reducing the sliding velocity), but at the expense of increasing friction and abrasive wear as theoretically demonstrated in previous studies [8,10,11]. The literature lacks a theoretical analysis on the mathematical optimization of sealing performance in terms of leakage, friction and wear This is covered in the present study for general macroscopic shape of hydraulic, polymeric, sliding seals. The latter requires reliable and precise modeling of wear, which is complicated as evidenced by previous attempts to validate numerical models [26]
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